1. Introduction
This invention relates to novel resins that are acid catalyzed reaction products of an aldehyde and an aromatic alcohol mixture consisting of a naphthol and a phenol.
2. Description of the Prior Art
The formation of phenolic resins by the condensation of a phenol with an aldehyde is well known in the art and described in numerous publications including Kirk-Othmer, Encyclopedia of Chemical Technology, Volume 15, pages 176 to 208, 1968, incorporated herein by reference. Phenol itself is the phenol used in the greatest volume for the formation of phenolic resins, but resorcinol, alkyl substituted phenols such as cresols, xylenols and p-tert-butylphenol and p-phenylphenol are also used in substantial volume. The aldehyde used is almost exclusively formaldehyde but small amounts of acetaldehyde and furfuraldehyde are also used.
The condensation of a phenol with an aldehyde can be an acid catalyzed reaction with a molar ratio of phenol to aldehyde less than 1 or an alkaline catalyzed reaction with a molar ratio of phenol to aldehyde greater than 1. The acid catalyzed reaction yields thermoplastic resins which have come to be known as the novolak resins while the alkaline catalyzed reaction yields thermosetting resins known as resole resins.
The novolak resins have many commercial uses. Their primary use is as a molding compound where they are molded to a desired configuration and then cured by cross-linking with a cross-linking agent such as hexamethylenetetramine. Another use of the novolak resins is as a film-forming material. For this use, the resin is applied from solution and usually is not cured following film formation.
Novolak resins, prior to cure, have moderate thermal stability and melt within a range of from about 90.degree. C. to 120.degree. C., dependent upon the composition of the resin and its molecular weight. There has been little effort to increase the thermal stability of the thermoplastic novolak resins because high thermal stability has not been considered to be an important property for a film-forming resin.